New DYNA Grip ^® Stay Cable Bridge in Austria

During 2009, steps were taken to improve flood protection in the municipalities of Bach and Elbingenalp in the Tyrolean Lech Valley. The construction of the Lech Bridge Bach was an important part of the first section of the B 198 federal road project. The new bridge became necessary because the existing arch bridge built in 1928 was no longer able to guarantee the required drainage volumes at high watermark.

According to project requirements, the supporting structure was to cross the river without any piers in the water, and the elevation of the existing bridge deck was eliminated in the new bridge to allow a level road layout. The new bridge was designed as a stay cable structure with one pylon and blends in well with the surrounding landscape. The main span is supported by six stay cables that fan out from the bridge’s center plane. An additional five parallel stay cables anchor the 19m high pylon into the abutment located behind it.

The bridge’s reinforced concrete supporting structure, which was constructed on false work, has a span length of 68m and a width of 11.10m. The upper part of the reinforced concrete pylon is designed as a composite steel hollow box that accommodates the stay cable anchorages.

For the new bridge, DSI supplied the DYNA Grip ^® stay cable system for 31 to 35 strands. This system permits both the replacement of individual strands and the replacement of complete stay cables.

The strands, which are galvanized, waxed and PE-coated, were installed from the superstructure into the pylon anchorage using a strand pusher. In order to guarantee the uniformity of individual strand forces within one stay cable, the post-tensioning levels, which were adjusted to suit the construction progress, were adjusted using the ConTen method. The newly developed ConTen valve was used in this process. Due to the limited space on site and an ambitious schedule, the installation of all of the stay cables and all of the post-tensioning works were planned and carried out in close cooperation with site management so that the new Lech Bridge was completed on schedule in the autumn of 2009.